Number the Stars

Read about the author, Lois Lowry.

Here's information and maps of Denmark from FactMonster.

Here's a map of Denmark and Sweden showing the route of rescue for Danish Jews.

Here's some information about the Nazi / German invasion of Denmark.

Here's a timeline of the Holocaust.

Here's some vocabulary from the book you should know:
lanky
obstinate
trousseau
ration
kroner
swastika
curfew
exasperated
synagogue
staccato
condescending
typhus
tantalize
permeate